Tcl glob Command

last modified October 20, 2026

The Tcl glob command is used to match file names against patterns. It returns a list of files that match specified patterns. This is useful for file operations and directory listings.

Basic Definition

The glob command expands wildcard patterns to match file names. It supports various pattern matching characters similar to Unix shell globbing.

Syntax: glob ?switches? pattern ?pattern ...?. The command returns a list of files matching the pattern(s); at least one pattern is required. The common switches are -nocomplain, -directory, -types, -tails, -join and -- (end of switches).

Basic File Matching

This example shows the simplest usage of glob to list all .tcl files in the current directory.

basic_glob.tcl

set tcl_files [glob *.tcl]
puts "Tcl files: $tcl_files"

The pattern *.tcl matches all files ending with .tcl. The result is stored in tcl_files and printed. On Linux the match is case-sensitive; Windows file systems are case-insensitive. If no file matches, glob raises an error unless -nocomplain is used.

Multiple Patterns

glob accepts any number of patterns as separate arguments.

multi_pattern.tcl

set files [glob *.tcl *.txt]
puts "Matching files: $files"

This matches both .tcl and .txt files. The result is a combined list of all files matching either pattern. The order of the result isn't guaranteed, and an error is raised only if none of the patterns match anything.

Hidden Files

By default, a wildcard in glob does not match a leading dot, so hidden files are not returned by *; the dot must be written in the pattern.

hidden_files.tcl

set hidden_files [glob -nocomplain .*]
puts "Hidden files: $hidden_files"

The .* pattern matches hidden files, and also the special entries . and .., which is why the output shows them. The -nocomplain switch returns an empty list if no matches exist instead of raising an error. This directory contains no other hidden files.

Directory Recursion

The glob command does not descend into subdirectories by itself. A recursive search combines the -directory and -types switches with a procedure that calls itself.

recursive_glob.tcl

proc find_files {dir pattern} {
    set files [glob -nocomplain -directory $dir -types f $pattern]
    foreach sub [glob -nocomplain -directory $dir -types d *] {
        lappend files {*}[find_files $sub $pattern]
    }
    return $files
}

puts "All Tcl files: [find_files . *.tcl]"

This finds all .tcl files in the current directory and its subdirectories. The procedure collects the matching files of a directory and then calls itself for each subdirectory. Hidden subdirectories are skipped, because the pattern * does not match a leading dot.

Type Filtering

The -types switch filters matches by file type (file, directory, etc).

type_filter.tcl

set directories [glob -nocomplain -types d *]
puts "Directories: $directories"

This lists only directories in the current folder; the output is empty here because the scratch folder has none. -types d matches directories, while -types f would match only plain files.

Case Insensitive Matching

The glob command has no case-insensitive switch, but character classes in the pattern can match both cases.

nocase_glob.tcl

set image_files [glob -nocomplain {*.[jJ][pP][gG]} {*.[pP][nN][gG]}]
puts "Image files: $image_files"

This matches .jpg/.JPG and .png/.PNG files regardless of case. The patterns are in braces so that Tcl does not treat the brackets as command substitution. Useful when dealing with files from different operating systems.

Best Practices

Error Handling: Use -nocomplain when matches might not exist.
Quoting: Put patterns with brackets in braces {} so that Tcl does not run them as commands.
Performance: Be cautious with recursive globs on large directories.
Platform: Remember that case sensitivity depends on the file system.
Sorting: Sort results if order matters in your application.

This tutorial covered the Tcl glob command with practical examples showing its usage in different file matching scenarios.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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